As is known in the art, the octane requirement is lower for a new or cleaned spark fired internal combustion engine than for one that has been subjected to operation over a period of time equivalent to several thousand miles. In other words, as a new or clean engine is used or operated an octane requirement increase (ORI) is observed, i.e., the octane number of the fuel required for knock-free operation of the engine increases over time until a stable level is reached. Also known is the fact that the observed octane requirement increase is associated with build-up of deposits in the combustion chamber of the engine. Consequently, additives have been employed for preventing or reducing deposit formation in or for removing the deposits from the combustion chamber once they have been formed. In this regard, see, for example, U.S. Pat. No. 4,357,148 and the patents cited therein.
Obviously, there is always a need for new, better and more economical additives which will function so as to reduce the octane requirement increase of spark ignition internal combustion engines.